AM modulated waveform

t0

dt

Y

The complex-valued time-domain data array. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

modulation index

The expected modulation index of the AM demodulated waveform parameter. This value is used to scale the AM demodulated waveform parameter.

Set this value to the estimated modulation index of the incoming AM modulated waveform signal to scale the AM demodulated waveform parameter by this value. The resulting scaled AM demodulated waveform can be used to quantify error between the actual and expected modulation index.

Set this value to 1.0 to return an AM demodulated waveform with no scaling. When you set suppressed carrier? to FALSE, the peak amplitude value of the unscaled AM demodulated waveform represents the true modulation index of the incoming AM modulated waveform.

Note

The node ignores the modulation index parameter if you set the suppressed carrier? to TRUE.

Default: 1.0

error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: no error

suppressed carrier?

A Boolean that determines whether the carrier has been suppressed in the incoming AM-DSB-modulated waveform.

Demodulation proceeds according to one of the following methods, depending on whether suppressed carrier? is set to TRUE or FALSE.

TRUE

The incoming baseband AM-DSBSC modulated signal
r
(
t
)
can be expressed as the following equations:

The incoming baseband AM-DSB modulated signal
r
(
t
)
can be expressed by the following equations:

r
(
t
)
=
s
D
S
B
(
t
)
e
j
φ
(
t
)

where
s
D
S
B
(
t
)
is a DSB modulated waveform and
φ
(
t
)
is any time-varying phase ambiguity. AM-DSB demodulation involves performing envelope detection. The AM demodulated waveform (t) is given by the following equation:

m
^
(
t
)
=
1
k
*
[
|
r
(
t
)
|
〈
|
r
(
t
)
|
〉
−
1
]

where
k
represents the modulation index.

Default: FALSE

AM demodulated waveform

The recovered message signal.

Note

Wire the AM demodulated waveform parameter to any LabVIEW waveform measurement node for further analysis. If the information signal is a single tone (normalized) and modulation index is set to 1.0 with suppressed carrier? set to FALSE, the peak amplitude value of the AM-demodulated waveform represents the true modulation index of the incoming AM-modulated waveform.